The invention relates to the field of textiles, or other sheet material, and more particularly to the winding or unwinding of a web of such material using a solid state take-up control to ensure uniform tension and reduced defects in the roll.
In the textile process of weaving cloth on a loom, the finished cloth is typically wound into a cloth roll upon leaving the loom. The cloth roll may be wound by a xe2x80x9ctake-upxe2x80x9d device either on the loom or off the loom. The present invention has particular advantages with an off-loom take-up. The off-loom take-up typically includes a pair of spaced take-up rollers which are driven by an electric drive motor through a speed reducer and a suitable drive, such as a chain and sprocket drive. The cloth roll is supported on the take-up rollers which rotate the cloth roll to take-up and form the cloth roll. It is important that the layers of the cloth roll are wound at a generally uniformed tension so that skewing and other undesirable characteristics of the cloth on the cloth roll are avoided.
Previously, various controls for the drive motor of the take-up rollers have been provided to impart desirable characteristics to the final cloth roll package. For example, U.S. Pat. No. 3,525,367, discloses an off-loom take-up having a tension control apparatus which selectively controls the linear rate of the warp yarn fed to the loom to automatically maintain a predetermined amount of tension on the warp yarns, and also maintain a uniform tension on the woven cloth coming from the loom as it is wound on the cloth take-up device. The cloth roll is supported on a cradle provided by spaced take-up rollers upon which the cloth roll is rotated and wound. For this purpose, the drive motor for the take-up rollers is provided so that the torque output of the motor is controlled. As the windings of the cloth roll accumulate, the increased loading on a driven take-up roller and drive motor is continuously sensed, and the torque output of the drive motor is continuously adjusted to maintain a preset fabric tension level.
U.S. Pat. No. 4,146,190, also discloses a control system for an off-loom take-up wherein an additional improvement is sought by using a spring biased dancer roll about which the cloth passes prior to reaching the cloth take-up roll Tension variations in the cloth are sensed at a point between the loom and the cloth roll, rather than at the driven take-up rollers. The tension variations cause the dancer roll to move up and down. The dancer roll is supported by spaced arms affixed to a control shaft which pivots in oscillations. A mechanical chain and sprocket drive transmits oscillations of the control shaft to a variable transformer which varies the voltage signal to the drive motor. The motor control varies the output torque of a variable torque drive motor for maintaining tension in the cloth within a desired range. U.S. Pat. No. 4,216,804, discloses a similar arrangement except that the sensing device, which is also in the form of a dancer roll carried on pivotal arms, eliminates the spring-biasing of the dancer roll, and utilizes gravity instead. In this case, the dancer roll rests on the cloth and is operated by gravity only to vary the torque output of the drive motor in response to tension variations. In this manner, a very light sensitivity is said to be provided which is advantageous in maintaining a preset fabric tension level for very lightweight fabrics. The gravity-type dancer roll continuously varies the motor control to vary the torque output of the drive motor much like U.S. Pat. No. 4,146,190. In these later two patents, variations in cloth tension are continuously sensed by the pivoting dancer roll. In turn, the pivotal movement of the dancer roll continuously varies a variable transformer which continuously varies a voltage signal to the drive motor. For example, in U.S. Pat. No. 4,216,804, a control shaft connected to the spaced pivotal arms which support the dancer roll includes a drive sprocket affixed to one end. A mechanical chain and sprocket drive includes a chain connected to a drive sprocket on an oscillating control shaft of the dancer roll and, to a drive sprocket of a variable transformer. Thus the movements of the dancer roll is mechanically transmitted by the chain and sprocket drive to the motor control to continuously vary the voltage signal and the output torque of the drive motor. While some advantages are afforded by the continuous and variable torque control, other problems are encountered by the need to have continuously moving mechanical and electrical parts. For example, the variable transformer (or rheostat) often forms a weak link in the control system because the small variations in movement of the dancer roll causes the wiper arm of the variable transformer to more or less continuously wipe over the same portion of the transformer windings. Eventually, this may cause the windings to short and the drive to fail. In this case, not only is down time required to replace the transformer device, and repair the control system, but cloth irregularities occur. Moreover, it has been thought that by continuously varying the control signal, possible over control of the system occurs resulting in a telescoping effect in the cloth roll taken up. Certain windings of the cloth roll project relative to other windings in the cloth roll causing undesirable characteristics.
Other controls have also been employed in off-loom take-ups. For example, U.S. Pat. No. 4,633,914, discloses a motor control for an off-loom take-up which detects an unusually high tension in a cloth web being taken up to terminate the take-up drive to prevent stretching and necking of the fabric being handled. The sensing device provides a time delay between sensing of the high tension and termination of the take-up drive. U.S. Pat. No. 5,415,207 discloses an apparatus and method for controlling the drive of an off loom take-up wherein the motor controller controls an electric motor which drives the driven take-up rollers at a preset speed which allows the cloth to travel at the directional speed at which the cloth travels leaving the take-rolls of the loom. This establishes a predetermined downward xe2x80x9ccreepxe2x80x9d in the movement of the pivotal directional roll. The downward movement of the directional roll is sensed by a detector. When the directional roll descends a prescribed distance, the detector momentarily sends a high speed signal to the drive motor which momentarily sends a high speed signal to the drive motor which momentarily steps up the speed of the drive motor and the cloth roll being to take out the slack of the cloth. The present speed is resumed and the high speed signal is discontinued. While intermittent controls, such as high and low speed controls rather than continuously varying speed controls, been used for winding strand material such as wire and the like is shown in U.S. Pat. Nos. 2,104,656 and 2,509,250, these types of controls have not been typically incorporated in loom take-ups for cloth.
Accordingly, an object of the invention is to provide an apparatus and method for controlling the drive of an off-loom take-up in a simple and reliable manner to produce a uniform cloth roll.
Another object of the invention is to eliminate the need for continuous adjustment of a torque or speed output of a drive motor on an off-loom take-up, yet still provide a wound cloth roll of desired characteristics.
Another object of the invention is to provide a control system and method for an off-loom take-up which employs a solid-state electronics drive which eliminates the wear of mechanical parts utilized in previous, similar control devices.
Another object of the invention is to provide a control system and method for an off-loom take-up wherein the tension which the cloth is maintained uniform and an electronic limit processor is used to configure for abnormalities.
Another object of the present invention is to provide a control system and method for an off-loom take-up wherein a preset tension applied by dancer roll to the cloth being wound may be set at a desired value and thereafter maintained uniform during the wind-up process.
In taking up a web, such as a textile web, from the loom, it is necessary to control the speed of the take up roll being wound on the loom take up. Typically a pivotal dancer arm is utilized to control the speed of the take up roll. The web coming from the loom passes under the dancer roll, around an idler roll, and between two bed rolls as it forms the web take-up roll. The main objective is to maintain the tension on the web generally constant as it forms the take-up roll. The uniform tension eliminates stretch marks, breaking, and other irregularities in the web. In order to maintain the tension generally uniform during wind-up, it is necessary to take the cloth up at the same speed as it is coming off the loom. That is, the web passing between the bed rolls will be traveling at the same rate as it is coming off the loom. If the fabric is coming off of the loom faster than it is being taken up, then it is necessary to increase the speed of the take-up. If the loom speed has decreased, it is necessary to decrease the speed of the take-up. Normally a loom is driven at a constant speed, but due to malfunctions and other problems, the loom speed or output can vary. The speed of the web off the loom will also vary depending on the style of fabric being woven. Therefore, it is necessary that the take-up adjust automatically to the rate at which the cloth is woven and the speed it is taken off the loom.